Dayside Low Energy Electron Precipitation Driven by Hiss Waves in the Presence of Ionospheric Photoelectrons

As was demonstrated by many observations, hiss waves are often to observed in the dayside plasmasphere and plumes. Previous studies of hiss waves have been focused on the scattering of energetic electrons of 10–1,000 keV energies and only recently this focus was shifted to the energies below several keV down to the energies of tens of eV. These studies, however, did not include electrons of ionospheric origin photo‐ and secondary‐ electrons. The major focus of our study is dayside low energy electron precipitation driven by hiss waves in the presence of ionospheric photo‐ and secondary‐ electrons. It is found that photoelectrons play an important role in hiss waves driven low energy electron precipitation phenomena. They are serving as the seed population that is required to study the low energy (below 1 keV) electrons using different kinetic approaches that are considered in this study. Our approach is based two kinetic codes: the SuperThermal Electron Transport (STET) and Fokker Plank (F‐P) models. The STET code couples magnetospheric hiss‐driven electron precipitation dynamic with ionosphere and forms the low energy MI coupling input to the F‐P code. The latter finalizes the formation of electron distribution function at magnetospheric altitudes via Landau resonant heating and forms the combined electron distribution function that is driven by Magnetosphere‐Ionosphere (MI) energy interplay processes. Plain Language Summary Magnetospheric hiss waves play a very important role in radiation belt dynamics. They scatter electrons toward the atmospheric altitudes and create the slot region that separates the inner and outer radiation belts. The radiation belt electrons at 10 keV–1 MeV energies are subject to efficient pitch angle scattering loss due to hiss waves in a timescale of several hours to days. In addition to the precipitation of energetic electrons, hiss waves could also cause the suprathermal electron heating at the energies from tens of eV to ∼1 keV, redistributing the electrons from the higher pitch angle and lower energy regime to the lower pitch angle and higher energy regime in a timescale of less than 1 hr. For the first time, this effect is evaluated in the presence of ionospheric photoelectrons based on the energy interplay between the magnetosphere and the ionosphere. It is found that the ionospheric photoelectron population can be considered as the seed population of lower energy magnetospheric electrons that are measured by Van Allen Pro